The present invention relates to a protection relay device for the distribution equipment of a distribution system having a hierarchy of branches.
FIG. 5 is a diagram showing the system structure of the conventional distribution system described in the Institute of Electric Engineers of Japan, Technical Study Report, No. 469, p 28, which uses a timing different protection relay device and has a hierarchy of branches coupled to a power source. This distribution system includes branches 8 to 10 of the hierarchy structure coupled to a power source 1, a current transformer 4A for detecting total current flowing through the higher-rank branch 8, and a relay 3A which determines whether or not a short-circuit failure has occurred in a path from the higher-rank branch 8 to the downstream thereof on the basis or current value detected by the current transformer 4A and operates a breaker 2A for cutting off the current flowing through the higher-rank branch 8 at the time where it is determined that the short-circuit failure has occurred in the path.
This distribution system further includes a current transformer 4B for detecting total current flowing through the middle-rank branch 9, and a relay 3B which determines whether or not a short-circuit failure has occurred in a path from the middle-rank branch 9 downstream thereof on the basis of the current value detected by the current transformer 4B and operates a breaker 2B for cutting off the current flowing through the middle-rank branch 9 at the time where it is determined that the short-circuit failure has occurred in the path. Further, this distribution system includes a current transformer 4D for detecting total current flowing through the lower-rank branch 10, and a relay 3D which determines whether or not a short-circuit failure has occurred in a path from the lower-rank branch 10 or downstream-thereof on the basis of the current value detected by the current transformer 4D and operates a breaker 2D for cutting off the current flowing through the lower-rank branch 10 at the time where it is determined that the short-circuit failure has occurred in the path.
This distribution system further includes a current transformer 4E for detecting total current flowing through a lower-rank branch end 11, and a relay 3E which determines whether or not a short-circuit failure has occurred at the lower-rank branch end 11 on the basis of the current value detected by the current transformer 4E and operates a breaker 2E for cutting off the current flowing through the lower-rank branch end 11 at the time where it is determined that the short-circuit failure has occurred in the lower-rank branch end.
This distribution system further includes a current transformer 4C for detecting current flowing through the predetermined position of a system branched from the higher-rank branch 8, and a relay 3C which determines whether or not a short-circuit failure has occurred in a path from the predetermined position or downstream thereof on the basis of the current value detected by the current transformer 4C and operates a breaker 2C for cutting off the current flowing through the predetermined position at the time where it is determined that the short-circuit failure has occurred in the path. Further, this distribution system includes a current transformer 4F for detecting current flowing through another predetermined position downstream of the predetermined position, and a relay 3F which determines whether or not a short-circuit failure has occurred in a path from the another predetermined position or downstream thereof on the basis of the current value detected by the current transformer 4F and operates a breaker 2F for cutting off the current flowing through the another predetermined position at the time where it is determined that the short-circuit failure has occurred in the path.
According to the distribution system thus arranged, the relays 3A to 3F are arranged to have different time periods for starting the operations after the occurrence of the short-circuit failure in accordance with the corresponding ranks of the system branches 8 to 10 thereby to discriminate the section where the short-circuit failure occurred, respectively.
For example, the operation time period required for operating (current cut-off operating) the corresponding one of the breakers 2A to 2F after the detection of the same current is set to be longest in the relay 3A which is closest to the power source 1 and shortest in the relays 3D, 3E and 3F which are disposed at the lower-rank end.
Thus, when the short-circuit failure occurs, the breaker at the higher-rank side among the breakers closest to the section where the short-circuit failure has occurred operates at first thereby to cut off the current supplied from the power source 1. For example, when the short-circuit failure occurs at the lower-rank branch 10 of the relay 3D, although each of the relays 3A, 3B and 3D detects the excessive current, the relay 3D having the shortest operation time operates the breaker 2D to cut off the current at the earliest time point as compared with other relays.
Further, when the short-circuit failure occurs at the higher-rank branch 8 between the relay 3A and the relay 3B, the relay 3A detects the excessive current and operates the breaker 2A to cut off the current upon the lapse of the set operation time period.
In the aforesaid conventional protection relay device for distribution equipment, when a short-circuit failure occurs at the higher-rank branch 8 nearest to the power source 1, a large excessive current is generated and such phenomena as a voltage drop, an instantaneous power failure or the like influences a wide area of the lower-rank system. However, since the operation time period of the relay 3A is set to be longest, the time period required for the breaker 2A to operate after the occurrence of the short-circuit failure is long.
As a consequence, there arises a problem that the short-circuit failure continues for a long time and so the distribution equipment may be broken and the operation of the devices connected to the distribution equipment may be stopped.
Further, in the case where the number of the branches of the system increases, there arises a problem that, since the operation of the breakers of the higher-rank is further delayed, it is required to adjust the operation time periods of all the relays again.
As a technique relating to the aforesaid protection relay device for a distribution equipment, the Unexamined Japanese Patent Application Publication No. Hei. 7-322470 discloses xe2x80x9cProtection Relay Central Management Devicexe2x80x9d wherein a central control device is coupled to a plurality of protection relays through a transmission path and the central control device collectively manages the operation states of the plurality of the protection relays. Further, as another technique relating to the aforesaid protection relay device for a distribution equipment, the Unexamined Japanese Patent Application Publication No. Sho. 58-119725 discloses xe2x80x9cProtection Relay System for Non-Utility Transformation Equipmentxe2x80x9d wherein a protection relay is disposed at a portion within premises, terminal devices are provided at various portions of the premises, the terminal devices send current and voltage information and breaker information to the protection relay, and the protection relay collectively performs the calculation for protecting the respective equipment within the premises to determine the breaker associated with the failure and to trip the breaker directly or through the terminal device.
The present invention has been made in view of the aforesaid conventional circumstances and an object of the invention is to provide a protection relay device for the distribution equipment which can determine a short-circuit failure section without differentiating the operation time periods among relays and remove the cause of the short-circuit failure quickly.
An object of the invention is to provide a protection relay device for the distribution equipment which can remove the cause of the short-circuit failure quickly without causing the delay of the detection of a short-circuit failure due to the transmission procedure of a transmission line.
An object of the invention is to provide a protection relay device for the distribution equipment which can remove the cause of the short-circuit failure quickly.
The protection relay device for the distribution equipment according to the invention is comprises:
breakers respectively disposed at branches of a distribution system having the branches of a hierarchy structure;
a plurality of relays respectively disposed at the branches, each of the plurality of relays detecting a short-circuit failure occurred at a lower-rank section thereof and outputting a detection signal; and
a central control device which receives the detection signals outputted from the plurality of relays, determines a short-circuit failure section where a short-circuit failure occurs on a basis of the detection signal thus received, and renders one of the plurality of relays of the branch corresponding to the short-circuit failure section thus determined to operate one of the breakers corresponding to the one of the plurality of relays.
A protection relay device for the distribution equipment according to the invention has the plurality of relays coupled to the central control device through a transmission path.
A protection relay device for the distribution equipment according to the invention has, in the central control device, a selection means for selecting the relay of the branch located at a lowest rank among the relays which outputted the detection signals received by the central control device as the relay of the branch located at a just higher rank of the short-circuit failure section, and a means for rendering the relay selected by the selection means to operate the breaker of the branch located at a just higher rank of the short-circuit failure section.
The protection relay device for the distribution equipment according to the invention a part or entirety of a transmission path shared by the plurality of relays, and the plurality of relays are arranged to have different sending start timings for starting sending of the detection signal that the sending start timings differ by 1 msec or less at every rank of the corresponding branch.
The protection relay device for the distribution equipment according to the invention has some or all of the breakers an interruption time of 20 msec or less.